Method of destroying growing weeds



United States Patent "ice 3,189,432 METHQD 0F DESTROYHJG GRQWFNG WEEDS Sidney B. Richter, Chicago, 111., assiguor to Veisicol Chemical Qorporation, Chicago, ill., a corporation of Illinois No Drawing. Uriginal application Oct. 15, 1958, Ser. No. 767,263. Divided and this application Dec. 18, 1961, Ser. No. 163,229

Claims. (Ci. 71--2.6)

H30 0 I CH3 will hereinafter be referred to as compound I. This chemical compound and its derivatives as cited above have marked activity as herbicides useful for the control of undesirable plant life.

Compound I can be prepared readily from the known starting material, 6-chloro-3-methoxytoluene, which itself can be obtained by chlorinating meta-cresol and methylating the resulting chloro compound with dimethyl sulfate. A chloromethyl group is then introduced into the 2-position of the 6-chloro-3-methoxytoluene by treating it with formaldehyde and hydrogen chloride. The chloromethylation reaction can be carried out using formaldehyde as a solution or in the forms of paraformaldehyde or trioxaue. Gaseous hydrogen chloride or concentrated hydrochloric acid can be used, and catalysts such as zinc chloride can be used to promote the reaction. The Z-chloromethyl-S-mcthoxy-6-chlorotoluene is then treated with a cyanide such as sodium cyanide in an inert solvent such as methanol or ethanol to convert it to the corresponding 2-cyanomethyl-3-methoxy-6-ch1oro toluene. Hydrolysis of the cyano compound in acid or basic media in the conventional manner produces the desired compound I, which is obtained in a form suitable for many herbicidal uses. However, compound I can be obtained in a pure state, if desired, by crystallization from a suitable solvent.

The anhydride of compound I is prepared by the removal of one molecule of water from two molecules of compound I as the free acid. In practice, it is convenient to prepare the anhydride by the acylation of the free carboxylic acid by its acid halide in the presence of a strong acylating agent such as pyridine. Thus a mixture of dry pyridine and dry benzene are treated with 1 mole of the acid chloride of compound I. The slightly exothermic reaction proceeds with the formation of an intermediate pyridinium salt. One mole of compound I as the ree acid is then added, the precipitate of pyridine hydrochloride is removed, and the anhydride of compound I is isolated by removal of the benzene.

The acid halide of compound I required in the above and other synthesis is prepared by the reaction of the free acid with a phosphorus trihalide in the conventional manner. Thus the treatment of compound I with phosphorus trichloride until the reaction ceases produces the acid chloride of compound 1.

Compounds Wmch are salts, esters, or amides of compound I can be prepared readily from the free acid. Thus treatment of the free acid with ammonium hy- Patented June 15, 1965 droxide gives a product which is the salt ammonium 2- methyl-3chloro-6-methoxyphenylacetate. Similarly, an alkali metal salt of compound I can be made by the treatment of the free acid with bases, such as the hydroxides, of a hall metals. Treatment of the acid with sodium hydroxide thus gives the salt sodium 2-methyl-3- chloro-o-methoxyphenylacetate as the product, while the use of potassium hydroxide gives the salt potassium 2- methyl-3-chloro-6-methoxyphenylacetate.

Amine salts of compound I are prepared by the addition of the free acid to various amines. Typical amines which can be used to prepare such amine salts are dimethylamine, trimethylamine, triethylamine, diethanolamine, triethanolamine, isopropylarnine, morpholine, and the like. The resulting products are, respectively, the dimcthylamine, trimethylamine, triethylamine, diethanolamine, triethanolamine, isopropylarn-ine, and morpholine salts of 2-methyl-3-chloro-6-methoxyphenylacetic acid.

Esters of compound I are prepared by the condensation of the acid with various alcohols. Thus the condensation of methyl alcohol with compound I gives the desired ester, methyl 2-methyi-3-chloro-6-methoxyphenylacetate.'

Other typical alcohols which can be used are propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, amyl, heXyl, heptyl, octyl, nonyl, decyl, and the like. The products are e corresponding alkyl esters of 2-methyl-3-chloro-6 methoxyphenylacetic acid. Although such complex esters are those prepared by the esterification of compound I with butoxyethanol, propylene glycol butyl ether, and the like are useful products in accordance with this invention,

preferred esters are those in which the esterifying group is.

an unsubstituted alkyl group which contains from 1 to 10 carbon atoms. The condensation of the acid with the alcohol is carried out suitably in an inert solvent such as an aromatic hydrocarbon and in the presence of a few percent by weight of an acid catalyst such as p-toluenesulfonic acid. The Water which forms during the esterification reaction can be removed continuously in many cases from the reaction mixture by distillation as it forms, and its volume can be measured to determine when the esterification is complete. distillation of the inert solvent.

Amides of compound I can be prepared conveniently by the reaction of the acid halide of compound I with ammonia or various amines. The reaction can be carried out in an inert solvent such as ether or benzene. Preferably two moles of the amine are used for each mole of the acid halide employed, since the hydrogen halide released during the reaction is taken up by some of the free amine which remains. The simplest amide, 2-methyl-3-chloro- 6-rnethoxyphenylacetamide, can be prepared by the reaction of the acid chloride of compound I with ammonia, either as the free gas or as an aqueous solution. This amide can also be prepared by hydrolysis of the corresponding nitrile. Substituted amides are prepared by the reaction of the acid halide of compound I with amines such as any of the primary or secondary amines suggested above for the preparation of the amine salts of compound I. Thus, for example, the reaction of the acid chloride of compound I with methylamine, butylamine, decylamine, or diethylarnine gives the N-methyl-, N-butyl-, N-decy1-, or N,N-diethyl-2-methyl-3-chloro-6-meth0xyphenylacetamides, respectively. While more complex amines such as the aromatic amines can be used as the amine reactant to give desirable products, which are specifically named as anilides, preferred amine reactants are alkylamines containin up to 10 carbon atoms.

For practical use as herbicides, the compounds of this invention are formulated with inert carriers to obtain proper concentrations and to facilitate handling. For exaisaisz The ester is then isolated by "higher the Concentration needed to kill them. Summer {annuals such as lambs-quarters,pigweeds, cocklebur, and

. ample, these compounds can be formulated into dusts by combining them with such inert substances as talc or clays.

The alkali metal salts of compound I are particularly suited to such dust formulations, and dusts containing from 5 to 25 ,percent by weight of active compound are convenient foruse in the field. The compounds of this The esters of compound Thecompounds of this invention can also be emulsified or suspended in water by the addition of emulsifiers and f wetting agents. The formulations of these active herbi cidal compounds are either applied directly to the plants ,to be controlled, or the soil in which the plants are growfing can betreated. Substances such as other pesticides, stabilizers, activators, synergists, 'spreaders and adhesives can be added to the formulations if desired. There is no significant difference in effect from the amount of water or organic solvent for diluting these herbicides, providing the same amount of chemical is'distributedevenly over a given area. ample, with low-pressure, low-volume sprays at the rate of about gallons of sprayper acre- Such distribution can be obtained, for ex- EXAMPLE 1 7 Preparation of 2-clzlor0metlzyZ-S-lfiethdxy-d-chlorotoluenc 6 chloro -3 methoxytoluene (1.66 moles which can be obtained, for example, as described by Peratoner and' Condorelli in Gazz. Chim. Ital., vol. 28, p. 213 (1898),

ismixed with 1 liter of concentrated hydrochloricacid and63 ml. (0.84 mole) of 37% formaldehyde solution in a 2-liter, 3-necked, round-bottomed flask fitted with a reflux condenser, mechanical stirrer, gas inlet tube, and

internal thermometer. The mixture is stirred and heated at a temperature of 55 C. for 3 hours while hydrogen chloride gas is passed into the mixture.

the reaction is continued for 3 hours. The mixture is then cooled and extracted with three 300-ml. portions or ether.v The ether extracts are Washed with water, 10%

- sodium bicarbonatesolution, and water, dried over mag- In-applying the herbicidal compounds, consideration if 'must be given ,to the nature and stage of growth of the 'crop, the species; of weeds present, the stage of growth of theweeds, environmental factors. influencing the rate and vigor of the weed growth, weather conditions at the time of application and immediately following, and the dosage. to be applied to a given area. Weeds are most susceptible when they are small and growing rapidly. Early applica-' .tion, therefore, results in'better control with less chemical j and increased yields because of the early destruction of the competing weeds. The larger and older the weeds the sunflower should .be sprayed whenthey are less than 4 incheshigh, NVinter annuals such as various mustards, fan-weed, yellow star-thistle, and wild radish are most easily killed while they are still in the rosette stage. 1 Usually weeds growing rapidly under optimum conditions "are relatively susceptiblegwhereas those growing under "adverse conditions tend. to be resistant to the herbicide sprays. 7

The efiectiveness of the compounds of this invention in small quantities makes them economically sound for weed control on large areas, with a great saving in labortcost, "in addition to corresponding cropincreases. These compounds are particularly valuable in weed control because l they are harmful to many weeds but harmless or relatively, harmless to some cultivated crops- Minute quantities in contact with plant tissues may be absorbed and translocated to all parts of'theplant, causing striking changes in the'form and functions and often resulting in their death. 1 The actual amount of compound to be used depends on a variety of factors but is influenced primarily by the species a of undesirable plant to'be controlled. Thus while nae-- tions of a pound of actual compound I or its equivalent f of an ester, salt, amide, or the anhydride of compound "I are often suflicient to post-emergence weed control on an' acre of corn, seed flax, perennial grass seed crops, j pastures'jor grazing areas (without legumes), wheat, and the like, the particular species of weeds encountered in evergreen and deciduous dormant nursery stock, nursery conifers, waste areas, woody brush, and the like may require the use'of one or more pounds of compound I or its derivatives per acre for good control. Dosage adjustmerits with the low-volume, low-pressure applications sug-' gested can he made by changing the nozzle size, nozzle V 3 hours.

, with a mechanicalstirrer and reflux condenser.

nesium sulfate, and filtered. Distillation of the ether and fractionation of the residue in vacuo gives the desired 2-ch1oromethyl-3-methoxy-fi-chlorotoluene.

EXAMPLE 2 Preparation. of Z-metlzylfi-chloro-(i-methoxypheny[acetic 1 acid (compound I ture is stirred and heated at reflux, and 2-chloromethyl-35 methoxy-6-chlorotoluene (0.90 mole). is added slowly in portions. The mixture is 'then stirredand refluxed for The cooled reaction mixture 'is extracted with three 300 ml. portions of ether. The ether extracts are washed with water,'dried over magnesium sulfate, and filtered. The ether is distilled off to give a residue of 2-cyanomethyl-3-rnetl1oxy-6-chlorotoluene.' A portion of this cyano compound (0.80 mole) is added slowly to a cooled mixture of 750 ml. of concentrated sulfuric acid and 900 ml, of water in a 3-liter, three-necked flask fitted Preparation of the sodium salt of compound 1 Compound I (0.5 mole) is dissolved in 500 cc. of

methanol and treated with a solution ofsodium hydroxide (20 g.; 0.5 mole) in'100 cc. of methanol. The methanol is removed by distillation in vacuo on the steam bath, and

EXAMPLE '4 7 Preparation of the ammonium salt of compound I V a Treatment of compound I (0.5 mole) in'500 cc. of

methanol with 34- cc. of commercial concentratedam monium hydroxide accordingto the method given in the a previous example gives the desired ammonium salt of compound I. a

' EXAMPLES Preparation of the dimethylamine sultof compoundl Compound I (0.5 mole) is dissolved in 500 cc. of dry ether and treated with dimethylamine (22.5 g.; 0.5 mole). The solid which separates is filtered, washed twice with An additional 63 ml. portion of formaldehyde solution is added, and

The

100 cc. portions of cold ether, filtered, pressed dry, and dried completely in a vacuum oven to give the desired dimethylamine salt of compound 1.

EXAMPLE 6 Preparation of the diethanolamine salt of compound I In the manner described in the previous example, compound I (0.5 mole) is treated with diethanolamine (52.5 g.; 0.5 mole) in 500 cc. of dry ether. The product which is isolated is the diethanolamine salt of compound 1.

EXAMPLE 7 Preparation of the morpholine salt of compound I Compound I (0.5 mole) is treated with morpholine (43.5 g.; 0.5 mole) in 500 cc. of ether, and the product is worked up as described for the preparation of the dimethylamine salt to give the desired morpholine salt of compound I.

EXAMPLE 8 Preparation of the ethyl ester of compound 1 Compound I (0.5 mole), ethyl alcohol (23 g.; 0.5 mole), and 3.0 g. of p-toluenesulfonic acid are dissolved in 500 ml. of benzene, and the solution is placed in a 1 liter, round-bottomed flask fitted with a reflux condenser and a calibrated Dean-Stark tube. The solution is heated at reflux temperature until 9 cc. of water have been collected in the Dean-Stark tube. The cooled reaction mixture is then extracted twice with 50-cc. portions of 10% sodium carbonate solution, and filtered. The benzene is distilled off in vacuo on the steam bath, and the residue is then distilled in vacuo to give the desired ethyl ester of compound 1.

EXAMPLE 9 Praparation of the decyl ester of compound I In the manner and apparatus described in the previous example, compound I (0.5 mole) and normal primary decyl alcohol (79 g.; 0.5 mole) are refluxed in 500 ml. of benzene in the presence of 3.0 g. of p-toluenesnltonic acid until 9 cc. of water have been distilled irom the reaction mixture. Work-up of the reaction mixture as described in the previous example gives the desired decyl ester of compound I.

EXAMPLE 10 Preparation of the n-butyl ester of compound I The reaction of compound I (0.5 mole) and n-butyl alcohol (37 g.; 0.5 mole) by the method described above for the preparation of the ethyl ester is used to prepare the n-butyl ester of compound 1.

EXAMPLE 11 Preparation of the acid chloride of compound I Compound I (1 mole) is placed with 500 cc. of dry benzene in a 2-liter, 3-necked, round-bottomed flask fitted with a mechanical stirrer, reflux condenser (calcium chloride tube), and dropping funnel. Phosphorus trichloride (123 g.; 0.9 mole) is added slowly dropwise with vigorous stirring while the reaction fiask is cooled with cold water if necessary to control the reaction. When all the PCl has been added and the evolution of hydrogen chloride has ceased, the reaction mixture i then transferred to distillation apparatus, and the solvent is distilled off. The residue is then distilled in vacuo to give the desired acid chloride of compound 1.

EXAMPLE 12 Preparation of the amide 0] compound I One mole of the acid chloride of compound I is placed with 500 cc. of dry benzene in a l-liter, 3-necked flask fitted with a reflux condenser, mechanical stirrer, and a gas inlet tube having a sparger tip. The mixture is stirred While dry ammonia ga is passed into the mixture for several hours. When the ammonia gas is no longer taken up, the precipitated salt is filtered off and extracted twice with ml. portions of ether. The ether extracts and benzene filtrate are dried over magnesium sulfate and filtered, and the solvents are distilled off to give the desired amide of compound I.

EXAMPLE 13 Preparation of the N -n-decylamide of compound I One mole of the acid chloride of compound I and 500 ml. of dry benzene are placed in a 2-liter, 3-necked, round-bottom flask fitted with a mechanical stirrer, reflux condenser, internal thermometer, and dropping funnel. n-Decylamine (314 g.; 2.0 moles) in 250 ml. benzene is added dropwise with vigorous stirring. When all the amine has been added, the reaction mixture is refiuxed for 2 hours and cooled, after which the precipitated salt is filtered off and extracted with two 100 ml. portions of ether. The ether extracts and benzene filtrate are dried over magnesium sulfate and filtered. Distillation of the solvents gives the desired N-n-decylamide of compound I.

EMMPLE 14 Preparation of the N,N-diethylamide of compound I One mole of the acid chloride of compound I is treated with diethylamine (146 g.; 2.0 moles) in the manner and apparatus described in the previous example to give the lxLN-diethylamide of compound 1.

EXAMPLE l5 Preparationof the anhydride of compound I ry pyridine (158 g.; 2.0 moles) and 1 liter of dry benzene are placed in a 2-liter, S-neclred, round-bottom flask fitted with a dropping funnel, mechanical stirrer, reflux condenser, and internal thermometer. One mole of the acid chloride of compound I, Which is prepared as described in a previous example, is added rapidly with stirring to the reaction mixture. Compound I (1 mole) is then added in portions over a period of about 10 minutes with rapid stirring. The pyridine hydrochloride which precipitates is filtered off, and the benzene is distilled from the filtrate in vacuo. The residue contains the desired anhydride of compound I, which can be purified by crystallization from a suitable solvent.

EXAMPLE 16 Percent Compound I 25 Antarox A-400 40 Methanol 35 Antarox A-400 is the trade name under which a nonionic detergent of the aromatic polyethylene glycol ether type is sold. The above concentrate is diluted with water to the desired concentration for use.

EXAMPLE 17 Preparation of an emulsifiable concentrate of the n-bzrtyl ester of compound I The following ingredients are mixed thoroughly in the given percentage proportions by weight:

Percent n-Butyl ester of compound I 59 Xylene l0 Triton X100 S Kerosene 26 Triton X-i 00 is the trade name under which an emulsifier of the alkyl aryl polyether alcohol type is sold. The

= and observed for response to treatment. I dicate a high order of herbicidal toxicity of the compounds of this invention.

' above'concentrate is diluted with water to the desired concentration for use.

' EXAMPLE 18 7 Preparation of a dztst from the sodium salt V of compound I V T he sodium salt of compound 1 (10% by Weight) and ,talc (99% by weight) are combined and ground to the i desired particle size in a mechanical grinder-blender.

' The herbicidal activity of chemical compounds is often The tomato plant The herbicidal activity of the compounds of this invennon; for example, can be demonstrated in greenhouse experiments on young potted tomato plants (Bonny Best j variety). The compounds are formulated into 10 percent 1 wettable powders and are dispersed in water at a concentration of 2,000 parts per million actual chemical. ;"Ten milliliters of an aliquot portion of the dispersion is added to the soil surface of the tomato plants, approximately 5 "to 7 inches tall. Inorderto avoid undue concentration oraccumulation of the chemical in any given area, 5 holes the size of a pencil and about 1 inch .deep are punched in the soil surface around the shoot, and the 10 milliliter application is divided equally among the 5 holes. Three plants are used for each application. 1 The treated plants are held under greenhouse conditions for 7 days, provided with subterranean-watering,

The results in- This application is a division of my co-pending application Serial No. 767,263, filed October 15, 1958, now

' abandoned.

I claim: 1. A method of destroying growing weeds-which com- ;prises contacting said weeds with a herbicidal composition comprising an inert carrier and as the essential active ingredient, in a quantity which is herbicidally toxic to said Weeds, a compound selected from the group consist- I ing of '2-methyl-3-chloro-6-methoxyphenylacetic' acid, its

:' anhydride, its alkali metal salts, its alkyl and alkanol i amine salts wherein the amine component contains up to ten carbon atoms, its ammonium salt, its morpholine sundae? r g salt, its estcrswherein the esterifying group is an unsub stituted alkyl containing from one to ten carbon atoms, its unsubstituted amide, and its alkyl; amides wherein the amine component contains up. to ten carbon atoms.

2. The method of claim Lwherein the compound is an alkali metal salt of Z-methyl-3-chloro-6 methoxypheny1- acetic acid.

3. The method of claim 1, wherein the compound is an alkyl amine salt of Z-methyl-Tachloro-6-methoxyphenylacetic acid in which the amine component contains up to ten carbon atoms. 7 r

4. The method of claim' 1, wherein'the compound is an valkanolamine salt of '2-methy1-3-ch-loro-6-methoxy phenylacetic acid'in which the amine component contains up to ten carbon atoms.

5. The method of claim 1, wherein the compound is a an ester of Z-methyl-Z-chloro-6-methoxyphenylacetic acid wherein the esterifying group is an unsubstituted alkyl containing from one to ten carbon atoms.

6. The method of claim 1, wherein the compound is an alkyl amide of Z-methyl-3 chioro-6-methoxyphenylacetic acid wherein the amine component contains up to ten carbon atoms.

7.'The method of claim 1, wherein the compound is 2 -methyl-3-chloro-6-methoxyphenylacetic acid.

8. The method of claim 1, wherein the compound is sodium 2.-methyl-3-chloro-6-methoxyphenylacetate.

9. The method claim 1, wherein the compound is the.

dimethylamine salt of 2-methyl-3-chloro-6-methoxyphenylacetic acid.

it The method of claim 1, wherein the compound is 'Z -methyl-3-chloro-6-methoxyphenylacetamide..

References Cited hytheEXaminer.

UNITED STATES PATENTS 2,394,916. 2/46 Iones 7152.6

2,580,459 1/52 Pappa et al. 26(l521 3/61 Tischler 71-2.6

MIA. BRINDISI, IRVING MARCUS, Lnwrs GOTTS,

V 'Examinefs.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,189,432 June 15, 1965 Sidney B. Richter It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, lines 18 to 23, the formula should appear as shown below instead of as in the patent:

CH COOH H CO CH column 5, line 36, for "Praparation", in italics, read Preparation in italics; column 8, line 28, after "method" insert of Signed and sealed this 7th day of December 1965.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. A METHOD OF DESTROYING GROWING WEEDS WHICH COMPRISES CONTACTING SAID WEEDS WITH A HERBICIDAL COMPOSITION COMPRISING AN INERT CARRIER AND AS THE ESSENTIAL ACTIVE INGREDIENT, IN A QUANTITY WHICH IS HERBICIDALLY TOXIC TO SAID WEEDS, A COMPOUND SELECTED FROM THE GROUP CONSISTING OF 2-METHYL-3-CHLORO-6-METHOXYPHENYLACETIC ACID, ITS ANHYDRIDE, ITS ALKALI METAL SALTS, ITS ALKYL AND ALKANOL AMINE SALTS WHEREIN THE AMINE COMPONENT CONTAINS UP TO TEN CARBON ATOMS, ITS AMMONIUM SALT, ITS MORPHOLINE SALT, ITS ESTERS WHEREIN THE ESTERIFYING GROUP IS AN UNSUBSTITUTED ALKYL CONTAINING FROM ONE TO TEN CARBON ATOMS, ITS UNSUBSTITUTED AMIDE, AND ITS ALKYL AMIDES WHEREIN THE AMINE COMPONENT CONTAINS UP TO TEN CARBON ATOMS. 